1. Field of the Invention
The present invention relates to a semiconductor device and, more particular, to a technique that increases reliability of a semiconductor device including an inter-level dielectric film made of a low dielectric constant dielectric film.
2. Description of the Related Art
In recent years, application of a so-called low dielectric constant dielectric film (Low-k film) having a dielectric constant lower than a commonly-used dielectric film and serving as a material of an inter-level dielectric film of a semiconductor device is proceeding in order to speed up the operation speed of the semiconductor device. The low-k film is obtained by, for example, reducing the density of a material to become a dielectric film, or removing polarity of a material to become a dielectric film. In the case of reducing the density (film density) of a material to become a dielectric film, a porous material is used in general. Therefore, in the low-k film, etching gas used at the time of forming a via hole or wiring groove in the film after formation of the dielectric film or moisture while the dielectric film being left to stand under the atmosphere penetrates into the film more easily as compared to a commonly-used dielectric film. Further, in the low-k film, deterioration (delamination and/or fracture) of a film material due to influence of working process is generated in the inside of the film more easily as compared to a commonly-used dielectric film.
As a result, the mechanical strength of a material itself is deteriorated (decreased) in the low-k film more than in a commonly-used dielectric film. Further, in so-called a low-k inter-level dielectric film obtained by stacking a plurality of low-k films, the bonding strength is deteriorated (decreased) at the interface between stacked low-k films or at the interface between the low-k film and other dielectric film is deteriorated (decreased) more than at the interface between commonly used dielectric films. The deterioration in the mechanical strength of the low-k film and the deterioration in the bonding strength at the interface between the low-k films or at the interface between the low-k film and other dielectric film pose a serious problem in implementing multilayer wiring structure in a semiconductor device as follows.
In order to solve the above deterioration in the mechanical strength (e.g. delamination and/or fracture) due to the use of the low-k film, a predetermined interface processing technique is applied, for example, in the formation process of the low-k film. Alternatively, when an RIE is performed to form a via hole or wring groove in the low-k film, its process is optimized. While the above measures can improve the mechanical strength of the low-k film and the bonding strength at the interface between the low-k films or between the low-k film and other dielectric film, a technique for further increasing the mechanical and bonding strength has now been demanded.